1. Technical Field
The present invention relates to reflective telescope systems and, more particularly, to nesting of two all-reflective afocal telescopes to provide four fields of view.
2. Discussion
When viewing a distance object through a telescope system, the observer is commonly interested in performing two separate and sequential functions. The first of these functions is a coarse search over a large field of view for the purpose of locating or acquiring previously undetected objects. The second function is the fine examination over a smaller field of view for the purpose of identification or discrimination of the previously located object.
It is desirable to have a single optical system which is capable of providing both the coarse search over a large field and the fine examination over a smaller field. An example of such a system is illustrated in U.S. Pat. No. 5,009,494, issued Apr. 23, 1991 to Iossi et al, entitled "Wide Field All-Reflective Multiple Field Of View Telescope", the specification and drawings of which are hereby expressly incorporated by reference. Here, a single optical system utilizes a pair of three-mirror astigmats which may be moved with respect to one another to provide a multiple field of view optical system. This invention provides a lower magnification, coarse resolution, wider field of view extreme to enable search and acquisition functions during operation of the system and also a higher magnification, finer resolution, narrower field of view to enable tracking and detailed imaging during the operation of the system. This system provides two fields of view.